DESCRIPTION: This project addresses key gaps in programmatic approaches to HIV testing to identify older children with undiagnosed HIV infection. There are 3.3 million HIV-infected children <15 years old globally, over 90% in Africa. Pediatric HIV treatment markedly lags adult treatment, in part due to children being undiagnosed. Children typically present when symptomatic at which time their survival, growth, and cognitive outcomes may have already been substantially compromised. In adult HIV, increasing implementation research is ongoing to optimize the treatment cascade from diagnosis to linkage and retention in care. However, similar pediatric HIV cascade research is lacking and is necessary to address specific challenges including lack of awareness that older children may have vertically transmitted HIV, parental misgivings about pediatric HIV testing and disclosure and systems that lack pediatric HIV testing protocols for older children. The HIV Counseling and Testing for Children at Home (CATCH) Study is a multi-disciplinary, implementation science, prospective cohort study. We will develop and optimize operational mechanisms to identify undiagnosed, asymptomatic HIV-infected children in Kenya and link them to HIV care. To find these undiagnosed children, we will access HIV-infected adults through HIV treatment centers and offer them the option of home-based (HBT) or clinic- based testing (CBT) for their children of unknown HIV status. We first aim to determine whether HBT or CBT results in a greater number of HIV-infected children identified and linked to care. Pediatric HIV test acceptance, location preference, and demographic characteristics will be assessed on 2,000 HIV-infected parents. Following testing, HIV-infected children identified by either HBT or CBT will be referred to care at the HIV care clinic of their choice; we will trace them at 6 and 12 months to determine linkage to HIV care, initiation of ART, retention, and survival. Secondly, we aim to characterize the structural, organizational, emotional, and cultural barriers and facilitators to pediatric HIV testing through series of 6 focus groups with health care workers and 30 in-depth interviews with HIV-infected parents and children to inform a thematic analysis of barriers and facilitators. The identified themes will refine the HBT and CBT testing models before implementation. Finally, we aim to test whether HBT or CBT is more cost-effective for identifying HIV- infected children. We will collect direct medical, direct non-medical, and indirect medical costs and perform an incremental cost-effectiveness analysis in terms of the number of children tested, number of HIV-infected children identified, and number of HIV-infected children liked to care. If determined to be acceptable, feasible, and cost-effective, targeted pediatric HBT or CBT may provide a new tool for identifying and linking to care asymptomatic HIV-infected older children in Africa, potentially limiting HIV-related morbidity and mortality and HIV transmission. Together, our aims will inform program implementers and policy-makers on optimal, sustainable approaches to diagnose and link children to care in high prevalence settings.